1. Field of the Invention
The present invention has to do with a method of preparing an inkjet ink imaged substrate such as a lithographic printing plate. More particularly, the present invention relates to a method of preparing a lithographic printing plate by providing a coated substrate, the coating of which is insolubilized by contact with an acidic medium. Selected portions of the coating are contacted with an acid delivered as an inkjet ink to produce insoluble regions. The remaining soluble regions of the coating may then be removed with a developer or fountain solution on a printing press to produce a lithographic printing plate.
2. Description of the Related Art
Several methods of preparing imaged lithographic printing plates based upon insolubilization of exposed regions are known in the art. The insolubilization can be achieved by a variety of reactions. A number of these methods use inkjet machines to deposit an ink-receptive image onto a hydrophilic substrate.
Published patent application No. U.S. 2003/0007052 A1 describes a method whereby a conventional negative lithographic coating which contains a diazonium condensate coated on a printing plate is selectively coated with alkaline inkjet ink to produce developer-insoluble imaged regions.
U.S. Pat. No. 6,472,054 describes a method of making a ready-to-use printing plate. An inkjet applies an acidic polymer, which is at least partially neutralized with a base, to a substrate. The polymer is dried after which the plate can be used without developing. A similar concept is described in U.S. Pat. No. 5,738,013 wherein an inkjet fluid is employed to apply an oleophilic image to a substrate.
U.S. Pat. No. 5,275,689 describes a method wherein an acid labile polymer is applied to a substrate and an inkjet is used to print a solution of organic acid and solvent thereon. Heat is applied to remove the solvent and then the plate is developed by washing away the solubilized acid labile polymer.
None of the related art discloses a method in which an acid delivered as an inkjet ink is employed to cross-link printed portions of a substrate to produce the inkjet ink imaged lithographic printing plates of the present invention.
Accordingly, it is an object of the present invention to provide a simple method of preparing a lithographic printing plate using commercial inkjet printers.